Tasco International 400 Series
The 400 series was Tasco's high end line around the 1970's, I believe. In addition to the models shown below, there were also wide angle 7x35's, #400 and #410. Common features included rubber eyecups and a focus wheel along the hinge.
#420 7x50 (left model in photo above)
Mfr: J-B160 (No J-E mark)
Date: circa 1970's
AFOV: ~77 degrees
TFOV: ~11 degrees, 578 feet at 1000 yards
Eye Relief: ~10mm
Prisms: high index
This wide angle glass produces what I would rate as only fair performance, with poor edge correction. Prism leakages are obvious, and vignetting is noticeable at the edge of field despite the use of high index prisms (probably due to undersized prisms). Even though the eyecups fold down, the eyepieces are recessed about 5mm, reducing the effective eye relief. The body of the 420 is shorter than that of the 430. As can be seen in the photo to the above right, the designers incorporated a focal reducer lens between the eyepiece and prism. This allows the use of a smaller eyepiece, but also results in less eye relief, poorer eyepiece correction (eyepiece performance decreases with the focal ratio), and extra light loss. This trick was also used in the Sears model #6276.
#430 10x50 (right model in photo at top)
Mfr: J-B160 (No J-E mark)
Date: circa 1970's
AFOV: ~72 degrees
TFOV: ~7.2 degrees, 380 feet at 1000 yards
Eye Relief: ~11mm
Prisms: high index
This model differs from the 420 in that it has rubber objective bumpers. It also has recessed eyepieces with somewhat tight eye relief. The image through the 430, however, is much preferable to the 420, with better overall correction, though there is still some prism leakage visible.